Makes about 2 1/4 cups. Published May 1, 2010. From Cook's Illustrated.

Cool the chocolate to between 85 and 100 degrees before adding it to the frosting. If the frosting seems too soft after adding the chocolate, chill it briefly in the refrigerator and then rewhip it until creamy. The frosting can be made up to 24 hours in advance and refrigerated in an airtight container. When ready to frost, place frosting in a microwave-safe container and warm briefly on high power until just slightly softened, 5 to 10 seconds. Once warmed, stir until creamy.

2. Place bowl in stand mixer fitted with whisk attachment. Beat mixture on medium speed until consistency of shaving cream and slightly cooled, 1 to 2 minutes. Add butter, 1 piece at a time, until smooth and creamy. (Frosting may look curdled after half of butter has been added; it will smooth with additional butter.) Once all butter is added, add vanilla and peanut butter; mix until combined. Increase speed to medium-high and beat until light, fluffy, and thoroughly combined, about 30 seconds, scraping beater and sides of bowl with rubber spatula as necessary.

Ingredients

Cool the chocolate to between 85 and 100 degrees before adding it to the frosting. If the frosting seems too soft after adding the chocolate, chill it briefly in the refrigerator and then rewhip it until creamy. The frosting can be made up to 24 hours in advance and refrigerated in an airtight container. When ready to frost, place frosting in a microwave-safe container and warm briefly on high power until just slightly softened, 5 to 10 seconds. Once warmed, stir until creamy. shopping list

2. Place bowl in stand mixer fitted with whisk attachment. Beat mixture on medium speed until consistency of shaving cream and slightly cooled, 1 to 2 minutes. Add butter, 1 piece at a time, until smooth and creamy. (frosting may look curdled after half of butter has been added; it will smooth with additional butter.) Once all butter is added, add vanilla and peanut butter; mix until combined. Increase speed to medium-high and beat until light, fluffy, and thoroughly combined, about 30 seconds, scraping beater and sides of bowl with rubber spatula as necessary. shopping list